The present invention relates to a method for forming grooves, for example longitudinal lubrication grooves, on the trunnions of a blank in which such trunnions are disposed radially about a central axis.
The present invention also relates to a method for manufacturing an element having radial trunnions provided with grooves.
The present invention further relates to a forming tool interposed between two press elements for forming grooves, for example lubrication grooves, in the radial trunnions of a blank.
Homokinetic joints are known which comprise elements having two, three or four radial cylindrical or spherical trunnions which are in smooth bearing relation to other elements of the force transmitting chain in the joint, for example rollers or roller segments rolling along axial inner raceways of a cylindrical part, or pivotal shoes or cups.
The capacity of these joints is markedly increased and their operating temperature reduced in an interesting manner when the trunnions are provided with lubrication grooves extending in a direction perpendicular to the mean direction of the relative movement between the bearing surfaces of each trunnion and the corresponding inner bearing surface of the force-transmitting element pivoting or oscillating on these trunnions.
It is consequently desirable to provide the active surface of these trunnions with lubrication grooves located in an axial plane of the trunnions substantially in alignment with the mean position of the load. Thus, the grooves must be located substantially in the poly-axial plane of the blank, i.e., the plane containing the axes of the individual trunnions perpendicular to the central axis of the trunnion element.
However, the great cost involved in the machining of such grooves in mass production by known means has been found to be dissuasive.